It's because when the rhs is a string, 'in' tests for a substring rather than simple containment. E.g. "ab" in "abc" gives True. So here 'in' is not a collection membership, it only operates on two strings.
On Tue, Apr 3, 2018 at 4:34 PM, Ethan Furman <et...@stoneleaf.us> wrote: > This behavior was recently brought to my attention [1]: > > --> 1 in 'hello' > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: 'in <string>' requires string as left operand, not int > > However, in any other collection (set, dict, list, tuple, etc), the answer > would be False. > > Does anyone remember the reason why an exception is raised in the string > instance instead of returning False? > > -- > ~Ethan~ > > > > [1] https://bugs.python.org/msg314900 > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: https://mail.python.org/mailman/options/python-dev/guido% > 40python.org > -- --Guido van Rossum (python.org/~guido)
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